In the control of the elevators in an elevator group, one objective is to ensure that customers are served in an optimal way in different traffic situations. A customer who presses an elevator call button should be served within a reasonable time both in peak-traffic conditions and during low-traffic hours. Various group control procedures are known which make use of traffic statistics for the control of the elevators or which involve monitoring of the waiting time of customers. A procedure used for group control, or more precisely speaking selection of traffic type in group control, is known from patent U.S. Pat. No. 5,229,559.
Previously known group control methods are not adaptable for situations in which the elevator users on a certain floor or certain floors are to be guaranteed a certain average or even above-average level of service. Especially during heavy traffic, e.g. upward and downward peak traffic, floors where the traffic is heavier than average may be ill served. This is because the number of people waiting behind the calls on each floor is generally not known.